Multiple beam range measurement process

ABSTRACT

In one general aspect, an apparatus can include a first laser subsystem configured to transmit a first laser beam at a first location on an object at a time and a second laser subsystem configured to transmit a second laser beam at a second location on the object at the time. The apparatus can include an analyzer configured to calculate a first velocity based on a first reflected laser beam reflected from the object in response to the first laser beam. The analyzer can be configured to calculate a second velocity based on a second reflected laser beam reflected from the object in response to the second laser beam. The first location can be targeted by the first laser subsystem and the second location can be targeted by the second laser subsystem such that the first velocity is substantially the same as the second velocity.

RELATED APPLICATION

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 14/994,998, filed Jan. 13, 2016, entitled“MULTIPLE BEAM RANGE MEASUREMENT PROCESS”, which claims priority to andthe benefit of U.S. Provisional Patent Application No. 62/102,901, filedon Jan. 13, 2015, which are incorporated herein by reference in theirentirety.

TECHNICAL FIELD

This description relates to a multiple beam laser LIght Detection AndRanging (LIDAR) system.

BACKGROUND

In some known LIDAR systems, a laser may be used to estimate range andvelocity of a moving object. However, known LIDAR systems used inmetrology are often relatively slow and inefficient. Thus, a need existsfor systems, methods, and apparatus to address the shortfalls of presenttechnology and to provide other new and innovative features.

SUMMARY

In one general aspect, an apparatus can include a first laser subsystemconfigured to transmit a first laser beam at a first location on anobject at a time and a second laser subsystem configured to transmit asecond laser beam at a second location on the object at the time. Theapparatus can include an analyzer configured to calculate a firstvelocity based on a first reflected laser beam reflected from the objectin response to the first laser beam. The analyzer can be configured tocalculate a second velocity based on a second reflected laser beamreflected from the object in response to the second laser beam. Thefirst location can be targeted by the first laser subsystem and thesecond location can be targeted by the second laser subsystem such thatthe first velocity is substantially the same as the second velocity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram that illustrates a laser system including multiplelaser subsystems.

FIG. 1B is a diagram that illustrates, in more detail, componentsincluded at least one of the laser subsystems shown in FIG. 1A.

FIG. 2 illustrates a process related to the embodiments describedherein.

DETAILED DESCRIPTION

FIG. 1A is a diagram that illustrates a laser system 100 (also can bereferred to as a LIght Detection And Ranging (LIDAR) system) configuredto use multiple laser subsystems 105A through 105N to produce or measureranges and/or velocities of an object 5 that can be stationary or movingwith respect to the laser system 100. In some implementations, themultiple laser systems 105A through 105N can be configured to transmitone or more laser beams. Accordingly, the laser system 100 can beconfigured to produce an array of lasers for, for example,characterization (e.g., measurement) of the object 5. In someimplementations, the object 5 can be referred to as a target or as atarget object 5. The laser system 100 can be used in frequency modulatedcontinuous wave (FMCW) applications. Such applications can includemetrology applications that include the characterization of surfaces(e.g., metal surfaces on vehicles (e.g., airplanes, automobiles, etc.)in a manufacturing environment).

The laser system 100 can implement a multiple beam range measurementprocess that can, for example, improve the speed and accuracy of rangemeasurements within FMCW applications. As a specific example, a singlesettling time for the simultaneous use of multiple lasers from the lasersystem 100 can result in measurement efficiencies over a system with asingle laser used multiple times where each use of the single laser isassociated with a settling time resulting in multiple settling times.The laser system 100 can also be configured to account for variousissues related to vibrations of the object 5 (which can be a rigid bodyobject or a non-rigid body object) that can result in inaccuracies incharacterization.

As shown in FIG. 1A, the LIDAR system 100 includes an analyzer 170configured to analyze data based on laser beams produced by the lasersubsystems 105A through 105N. In some implementations, the analyzing caninclude estimating a range and/or a velocity for one or more of thelaser subsystems 105A through 105N.

FIG. 1B is a diagram that illustrates, in more detail, componentsincluded at least one of the laser subsystems shown in FIG. 1A. Thelaser source 110 of the laser subsystem 105A is configured to emit(e.g., produce, propagate) electromagnetic radiation at one or morefrequencies that can be, for example, a coherent light emission (e.g.,monochromatic light emission) or beam. For simplicity, the emissionsfrom the laser source 110 will be referred to as an electromagneticradiation emission (such as electromagnetic radiation emission), anemitted laser signal 10, or as an emitted light.

As shown in FIG. 1B, the laser signal 10 can be split by the splitter125 into multiple laser signals such as at least laser signals 11-1 and11-2. In some implementations, the laser signal 11 can be derived from asplit laser signal and can be referred to as combined laser signal. Asshown in FIG. 1B, an interferometer can be used to produce the lasersignal 11, which may be analyzed for one or more corrections by theanalyzer 170 (which can also be referred to as a demodulator) shown inFIG. 1A. In such implementations, the laser signal 10 can be furthersplit (e.g., by splitter 125) into laser signal 11-1 and laser signal11-2. The laser signal 11-1 can be reflected from the object 5 as lasersignal 11-4. Laser signal 11-2 can be delayed by a delay 142C (which canbe correlated to a length) to laser signal 11-3 and laser signal 11-3can be combined with the laser signal 11-4 via a combiner 140C. Thelaser signal 11 (also can be referred to as an interferometer signal)from the interferometer can be used to gather information about thelaser signal 11 using a detector 150C. Discussions related to lasersignal 11 below can be applied to any of the component laser signals11-1 through 11-4 that can be used to define laser signal 11, which canbe the target laser signal or the laser signal targeted for analysis bythe analyzer 170. The splitter 125 is illustrated as a single componentfor simplicity. In some implementations, the splitter 125 can includemore than one splitter. Similarly one or more of the combiners shown inFIG. 1B may be combined or may include additional combiners.

As shown in FIG. 1B, the laser subsystem 105A includes a frequency sweepmodule 120 (which can be used with more than one laser subsystem). Thefrequency sweep module 120 is configured to trigger the laser source 110to produce a variety of optical frequencies (also can be referred togenerally as frequencies), for example, by modulating a drive current ofthe laser source 110. Specifically, the frequency sweep module 120 isconfigured to trigger laser source 110 to produce a pattern of opticalfrequencies (also can be referred to as a frequency pattern). Forexample, the frequency sweep module 120 can be configured to trigger thelaser source 110 to produce a sinusoidal wave pattern of opticalfrequencies, a sawtooth wave pattern of optical frequencies, and/or soforth. In some implementations, the sawtooth wave pattern can have aportion continuously increasing (e.g., monotonically increasing,linearly increasing, increasing nonlinearly) in optical frequency (alsocan be referred to as up-chirp) and can have a portion continuouslydecreasing (e.g., monotonically decreasing, linearly decreasing,decreasing nonlinearly) in optical frequency (also can be referred to asdown-chirp). Accordingly, the frequency pattern can have a cycleincluding an up-chirp and a down-chirp.

The laser subsystem 105A includes a combiner 140C configured to receivethe laser signal 11-4 reflected (also can be referred to as a reflectedlaser signal or as a scattered laser signal) (not shown) from the object5 in response to an emitted laser signal 11-1 (split from laser signal10) from the laser source 110 toward the object 5. In someimplementations, the reflected laser signal (also can be referred to asa return signal or return light) from the object 5 can be mixed with aportion of the emitted laser signal 10 (e.g., laser signal 11-3 delayedby delay 142C) and then analyzed by the analyzer 170 (after beingconverted to an electrical signal by detector 150C).

The analyzer 170 (which can be used with more than one laser subsystemand/or included within one or more of the laser subsystems) of the lasersubsystem 105A is configured to analyze a combination of emitted lasersignal 11-1 from the laser source 110 and reflected laser signal 11-4received by the combiner 140C. The emitted laser signal 11-1 can beemitted in accordance with a pattern including an up-chirp followed by adown-chirp (or a down-chirp followed by an up-chirp). The combination ofa frequency of the emitted laser signal 11-1 from the laser source 110and a frequency of the reflected laser signal 11-4 received by thecombiner 140C can be analyzed by the analyzer 170 to obtain or define abeat frequency or signal. In other words, the beat frequency can be asum of a signal frequency change over the round trip to the object 5(emitted laser signal) and back (reflected laser signal), and mayinclude a Doppler frequency shift of the reflected laser signalresulting from relative range motion between the laser subsystem 105Aand the object 5. In some implementations, the beat signal can have arelatively constant frequency or a varying frequency. In someimplementations, a combination of a frequency of emitted laser signal11-1 and a frequency of reflected laser signal 11-4 can be referred toas a difference frequency, a beat frequency or as a round-tripfrequency.

The analyzer 170 can be configured to calculate a round-trip timeperiod, which is a time period from the emission of the laser signal 10to receipt of the return of the reflected laser signal. A combination ofthe emitted later signal 11-1 and the reflected laser signal 11-4 cancollectively be referred to as a round-trip laser signal. The analyzer170 can also be configured to calculate a range and/or a velocity basedon the combination of the emitted laser signal 11-1 and the reflectedlaser signal 11-4.

The optical power of the laser output can change significantly during afrequency pattern such as a frequency sweep or up-chirp/down-chirp as aresult of, for example, drive current modulation of the laser source110. The frequency pattern may be non-ideal (e.g., may deviate) from aspecified frequency pattern because of an imperfect drive currentsignal, unavoidable thermal excitations in the laser source 110, and/orso forth that can cause variations, for example, frequency, phase,and/or so forth.

A linearly-chirped FMCW LIDAR can calculate a range by determining thefrequency of a delayed chirp that has traveled to the target (e.g.,object 5) and back relative to the frequency of a chirp that hasfollowed a local oscillator (LO) path within the LIDAR system 100. Insome implementations, the LO path can include the path between thesplitter 125 and the combiner 140C, which can include laser signal 11-2,the delay 142C, and laser signal 11-3. If the target signal is combinedwith (e.g., beat against) the LO signal then the frequency of the beatsignal will be the difference frequency resulting from the (Range−LO)delay:F=(2*Range−LO)*HZPM  Eq. (1)where, F=beat frequency, 2*Range=target round trip path length, LO=localoscillator path length, HZPM=(Hz/sec lidar chirp rate)/c, and c=velocityof light (meters/second).

As shown in FIG. 1B, the LO length is a length correlated to the delay142C. The (range−LO) term can represent a length difference associatedwith an interferometer signal derived from the laser signal 10. In otherwords, the range term can be a length associated with the laser signal10 that may include the distance to a target (e.g., object 5), and maybe a round-trip distance, and the LO term can be a length associatedwith a delayed version of the laser signal 10. Accordingly, the(range−LO) can represent a length derived from a beating of the lasersignal 10 and a delayed version of the laser signal 10.

If the target has a non-zero velocity component (linear motion orvibration) v in the direction of increasing range, as is generally thecase, the Eq. (1) becomes:F=(2*Range−LO)*HZPM+(v/c)*F0  Eq. (2)where F0 is the carrier frequency of the LIDAR laser=c/Lambda whereLambda is the laser wavelength. In some implementations, a variation inrange and/or velocity that can be tolerated can be calculated using Eq.(2). For example, a variation in range in can be calculated within aparticular threshold range based on a variation in velocity using Eq.(2). Accordingly, a tolerance in velocity (e.g., linear motion orvibration) variation can be determined for a given range variation.Similarly, a tolerance in range variation can be determined for a givenvelocity (e.g., linear motion or vibration) variation.

If the target is vibrating so that v=v(t), we have, to a closeapproximation:F(t)=(2*Range−LO)*HZPM+(v/c)*F0  Eq. (3)

If multiple simultaneous range measurements are made on a surface inclose proximity we will have approximately (if the LO paths are the sameand the velocities are the same at each position):F _(j)(t)=(2*Range_(j)−LO)*HZPM+(v/c)*F0  Eq. (4)In some implementations, the close proximity can be, for example, closeenough in proximity such that displacement due to vibration at each ofthe locations associated with the respective range measurements are thesame or at least linearly related.

The laser system 100 (and laser subsystem 105A, for example) describedabove with respect to FIGS. 1A and 1B can result in a variety ofefficiencies. For example, in some implementations, frequency at eachtime point is a sum of components proportional to range and velocity(which can be noise and can be associated with Doppler effects) in therange direction (e.g., range derivative). This concept is expressed inthe equations Eq. (1)-(3) above. These components alternate relativesign between upchirp and downchirp data points. In the absence of, forexample, a counter chirp LIDAR architecture, multiple time points areprocessed to determine range and velocity.

In some implementations, a differential equation can be solved todetermine the time histories of range and the range derivative. In someknown applications, such as in metrology applications, simpleapproximations can be made, such as constant velocity, to estimate rangeand velocity, or to average over time and assume that range is constantand velocity averages to zero. This approach can result in a slowmeasurement process in environments in which vibration is significant(the significance or tolerance which can be determined using, forexample, Eq. (2) as described above). In contrast, the LIDAR system 100with multiple lasers (e.g., closely-spaced laser beams) can greatlyaccelerate the measurement process, while yielding significantimprovements in relative and absolute range estimates and relativeazimuth and elevation estimates.

Specifically, in some implementations of the LIDAR system 100, absoluteand relative range accuracy improvement can be implemented because thevibration velocity field can be slowly varying as a function ofposition. Therefore, the velocity values (e.g., magnitudes) atrelatively closely spaced points will be nearly the same or, in theworst case, may be approximated as linearly varying in value as afunction of history and/or lateral distance. In some implementations,the velocity values at closely spaced points will be nearly the same or,in the worst case, may be approximated as linearly varying in value as afunction of x and y, if z is the Cartesian coordinate in the directionof the LIDAR beams. In some implementations, for a rigid solid object,instantaneous z-velocity can vary exactly linearly as a function of xand y. Therefore, the differential equations to be solved for range andvelocity time history at each point can be linked to each other. Bysolving for the range and velocity fields simultaneously there will be areduction in error. In some implementations of the LIDAR system 100, areduction in relative range error between local points can beimplemented because the points are measured simultaneously and thepossibility of range motion is eliminated. In some implementations, asubstantial reduction in relative azimuth and elevation error can existbetween local points because the relative azimuth and elevation of thesepoints results from the rigid structure of the multiple beam array ofthe LIDAR system 100. In some implementations, multiple measurements canbe performed simultaneously in the LIDAR system 100, which can result intime or speed efficiencies. For many metrology processes, features canbe measured by measuring many relatively closely spaced points. A speedadvantage can be obtained by measuring multiple points simultaneously.

In some implementations, the LIDAR system 100 can have multiple beamsfrom the laser subsystems 105A through 105N where simultaneousmeasurements using the multiple beams results in simultaneous estimatesof both range and/or velocity at each beam location, and the variousbeam locations are spatially close enough to have substantially the samevelocity (Doppler component). In other words, in some implementations,the LIDAR system 100 can have a first laser beam transmitted at a timeat a first location from the laser subsystems 105A and a second laserbeam transmitted at the same time from the laser subsystem 105N at asecond location where simultaneous measurements calculated using thefirst and second laser beams result in simultaneous estimates of bothrange and/or velocity at each of the first and second beam locations,and the first and second beam locations can be spatially close enoughsuch that Doppler shifts for the first and second laser beams may besubstantially the same or linearly related. In some implementations, themeasurements from the LIDAR system 100 can be processed together by theanalyzer 170 to estimate the constant or linearly varying velocity ofthe surface, and this estimated velocity can be used by the analyzer 170to correct the range estimates at each of the beam locations.

In some implementations, measurements at multiple times can be used bythe analyzer 170 to estimate a time history (e.g., evolution) of theranges and velocities to further improve the estimates of range (andvelocity). For example, a first set of simultaneous measurements at afirst time can be used by the analyzer 170 with a second set ofsimultaneous measurements at a second time to produce at least a portionof a time history of ranges and/or velocities. These different sets ofsimultaneous measurements can be used by the analyzer 170 to furtherimprove estimates of the ranges and/or velocities.

In some implementations, the LIDAR system 100 can be configured suchthat multiple simultaneous measurements at points at a particular timeproduced by the LIDAR system 100 can be used by the analyzer 170 toimprove relative range between the points at the particular timeindependent of absolute range accuracy. We can rearrange equation 2 toyieldRange=(F/HZPM+LO)/2−(v/c)*F0/HZPM/2  Eq. (5)

For each beam. The relative range for each measurement is the differencebetween these measurements, so that if v is the same for each beam, thenthe relative range does not depend on the velocity.

In some implementations, the LIDAR system 100 can be configured suchthat a rigid physical structure defines the relative positions of themultiple beam array produced by the laser subsystems 105A through 105Nof the LIDAR system 100. This known set of relative positions can beused by the analyzer 170 to produce improved relative measurements of x,y, and/or z locations of each of the measured points by the lasersubsystems 105A through 105N.

In some implementations, the LIDAR system 100 can have an increasedusable data rate because multiple points can be measured simultaneously,each point can have increased absolute accuracy, and/or each point canhave increased relative accuracy as described above.

FIG. 2 illustrates a process related to the embodiments describedherein. As shown in the flowchart, a first laser beam is transmitted ata first location on an object at a time (block 200). The first laserbeam can be transmitted by a first laser subsystem (e.g., one of thelaser subsystems 105). A second laser beam is transmitted at a secondlocation on the object at the time (e.g., at the same time) (block 210).The second laser beam can be transmitted by a second laser subsystem.

As shown in FIG. 2 , a first velocity at the first location iscalculated based on a first reflected laser beam reflected from theobject in response to the first laser beam (block 220). The calculationscan be performed by an analyzer (e.g., the analyzer 170). In someimplementations, a first range can be calculated at the first locationbased on the first reflected laser beam.

A second velocity at the second location is calculated based on a secondreflected laser beam reflected from the object in response to the secondlaser beam where the first location can have a proximity to the secondlocation such that the first velocity is linearly related to the secondvelocity (block 230). The calculations can be performed by an analyzer.In some implementations, a second range can be calculated at the secondlocation based on the second reflected laser beam.

In some implementations, one or more portions of the components shownin, for example, the laser system 100 and/or the laser subsystem 105A inFIGS. 1A and 1B can be, or can include, a hardware-based module (e.g., adigital signal processor (DSP), a field programmable gate array (FPGA),a memory), a firmware module, and/or a software-based module (e.g., amodule of computer code, a set of computer-readable instructions thatcan be executed at a computer). For example, in some implementations,one or more portions of the laser subsystem 105A can be, or can include,a software module configured for execution by at least one processor(not shown). In some implementations, the functionality of thecomponents can be included in different modules and/or differentcomponents than those shown in FIGS. 1A and 1B.

In some embodiments, one or more of the components of the lasersubsystem 105A can be, or can include, processors configured to processinstructions stored in a memory. For example, the analyzer 170 (and/or aportion thereof) can be a combination of a processor and a memoryconfigured to execute instructions related to a process to implement oneor more functions.

Although not shown, in some implementations, the components of the lasersubsystem 105A (or portions thereof) can be configured to operatewithin, for example, a data center (e.g., a cloud computingenvironment), a computer system, one or more server/host devices, and/orso forth. In some implementations, the components of the laser subsystem105A (or portions thereof) can be configured to operate within anetwork. Thus, the laser subsystem 105A (or portions thereof) can beconfigured to function within various types of network environments thatcan include one or more devices and/or one or more server devices. Forexample, the network can be, or can include, a local area network (LAN),a wide area network (WAN), and/or so forth. The network can be, or caninclude, a wireless network and/or wireless network implemented using,for example, gateway devices, bridges, switches, and/or so forth. Thenetwork can include one or more segments and/or can have portions basedon various protocols such as Internet Protocol (IP) and/or a proprietaryprotocol. The network can include at least a portion of the Internet.

In some implementations, a memory can be any type of memory such as arandom-access memory, a disk drive memory, flash memory, and/or soforth. In some implementations, the memory can be implemented as morethan one memory component (e.g., more than one RAM component or diskdrive memory) associated with the components of the laser subsystem105A.

Implementations of the various techniques described herein may beimplemented in digital electronic circuitry, or in computer hardware,firmware, software, or in combinations of them. Implementations mayimplemented as a computer program product, i.e., a computer programtangibly embodied in an information carrier, e.g., in a machine-readablestorage device (computer-readable medium, a non-transitorycomputer-readable storage medium, a tangible computer-readable storagemedium) or in a propagated signal, for processing by, or to control theoperation of, data processing apparatus, e.g., a programmable processor,a computer, or multiple computers. A computer program, such as thecomputer program(s) described above, can be written in any form ofprogramming language, including compiled or interpreted languages, andcan be deployed in any form, including as a stand-alone program or as amodule, component, subroutine, or other unit suitable for use in acomputing environment. A computer program can be deployed to beprocessed on one computer or on multiple computers at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

Method steps may be performed by one or more programmable processorsexecuting a computer program to perform functions by operating on inputdata and generating output. Method steps also may be performed by, andan apparatus may be implemented as, special purpose logic circuitry,e.g., an FPGA (field programmable gate array) or an ASIC(application-specific integrated circuit).

Processors suitable for the processing of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. Elements of a computer may include atleast one processor for executing instructions and one or more memorydevices for storing instructions and data. Generally, a computer alsomay include, or be operatively coupled to receive data from or transferdata to, or both, one or more mass storage devices for storing data,e.g., magnetic, magneto-optical disks, or optical disks. Informationcarriers suitable for embodying computer program instructions and datainclude all forms of non-volatile memory, including by way of examplesemiconductor memory devices, e.g., EPROM, EEPROM, and flash memorydevices; magnetic disks, e.g., internal hard disks or removable disks;magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor andthe memory may be supplemented by, or incorporated in special purposelogic circuitry.

To provide for interaction with a user, implementations may beimplemented on a computer having a display device, e.g., a liquidcrystal display (LCD) monitor, for displaying information to the userand a keyboard and a pointing device, e.g., a mouse or a trackball, bywhich the user can provide input to the computer. Other kinds of devicescan be used to provide for interaction with a user as well; for example,feedback provided to the user can be any form of sensory feedback, e.g.,visual feedback, auditory feedback, or tactile feedback; and input fromthe user can be received in any form, including acoustic, speech, ortactile input.

Implementations may be implemented in a computing system that includes aback-end component, e.g., as a data server, or that includes amiddleware component, e.g., an application server, or that includes afront-end component, e.g., a client computer having a graphical userinterface or a Web browser through which a user can interact with animplementation, or any combination of such back-end, middleware, orfront-end components. Components may be interconnected by any form ormedium of digital data communication, e.g., a communication network.Examples of communication networks include a local area network (LAN)and a wide area network (WAN), e.g., the Internet.

While certain features of the described implementations have beenillustrated as described herein, many modifications, substitutions,changes and equivalents will now occur to those skilled in the art. Itis, therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the scope of theimplementations. It should be understood that they have been presentedby way of example only, not limitation, and various changes in form anddetails may be made. Any portion of the apparatus and/or methodsdescribed herein may be combined in any combination, except mutuallyexclusive combinations. The implementations described herein can includevarious combinations and/or sub-combinations of the functions,components and/or features of the different implementations described.

What is claimed is:
 1. A LIght Detection And Ranging (LIDAR) system,comprising: a first laser subsystem configured to transmit a first laserbeam at a first location on an object at a time; a second lasersubsystem configured to transmit a second laser beam at a secondlocation on the object at the time; and an analyzer configured toanalyze data based on laser beams produced by the LIDAR system, theanalyzer configured to calculate a first range based on a firstreflected laser beam reflected from the object in response to the firstlaser beam, the analyzer configured to calculate a second range based ona second reflected laser beam reflected from the object in response tothe second laser beam, the analyzer configured to detect a vibrationvelocity field over the object; the first location being targeted by thefirst laser subsystem and the second location being targeted by thesecond laser subsystem such that a first displacement due to thevibration velocity field at the first location is substantially the sameas a second displacement due to the vibration velocity field at thesecond location while the vibration velocity field is being detected. 2.The LIDAR system of claim 1, wherein the first range and the secondrange correspond with the time.
 3. The LIDAR system of claim 1, whereinthe first laser subsystem includes a laser source, a splitter and adelay, the splitter being disposed between the laser source and thedelay.
 4. The LIDAR system of claim 1, wherein the first laser subsystemincludes a laser source, a delay and a combiner, the delay beingdisposed between the combiner and the laser source.
 5. The LIDAR systemof claim 1, wherein the analyzer is configured to calculate a constantvelocity of a surface of the object, the analyzer is configured tocorrect a first displacement based on the constant velocity of thesurface.
 6. The LIDAR system of claim 1, wherein the analyzer isconfigured to calculate a varying velocity of a surface of the object,the analyzer is configured to correct the second range based on thevarying velocity of the surface.
 7. The LIDAR system of claim 1, whereinthe first range and the second range are included in a first set ofsimultaneous measurements, the time is a first time, the first lasersubsystem configured to transmit a third laser beam at a third locationon the object at a second time; the second laser subsystem configured totransmit a fourth laser beam at a fourth location on the object at thesecond time, the analyzer configured to calculate a third range based ona third reflected laser beam from the third laser beam, the analyzerconfigured to calculate a fourth range based on a fourth reflected laserbeam from the fourth laser beam, the third range and the fourth rangeare included in a second set of simultaneous measurements, the analyzerconfigured to modify the first range based on first set of simultaneousmeasurements and the second set of simultaneous measurements.
 8. TheLIDAR system of claim 1, wherein the first range is a first estimatedrange calculated based on the first reflected laser beam and the secondrange is a second estimated range calculated based on the firstreflected laser beam and the second reflected laser beam.
 9. A LIghtDetection And Ranging (LIDAR) system, comprising: a first lasersubsystem configured to transmit a first laser beam at a first locationon an object at a time; a second laser subsystem configured to transmita second laser beam at a second location on the object at the time; andan analyzer configured to analyze data based on laser beams produced bythe LIDAR system, the analyzer configured to calculate a first rangebased on a first reflected laser beam reflected from the object inresponse to the first laser beam, the analyzer configured to calculate asecond range based on a second reflected laser beam reflected from theobject in response to the second laser beam, the analyzer configured todetect a vibration velocity field over the object, the first locationhaving a proximity to the second location such that a first displacementdue to the vibration velocity field at the first location is linearlyrelated to a second displacement due to the vibration velocity field atthe first location while the vibration velocity field is being detected.10. The LIDAR system of claim 9, wherein the analyzer is furtherconfigured to calculate a constant velocity of a surface of the object,the analyzer is configured to correct the first range based on theconstant velocity of the surface.
 11. The LIDAR system of claim 9,wherein the analyzer is further configured to calculate a varyingvelocity of a surface of the object, the analyzer is configured tocorrect the first range based on the varying velocity of the surface.12. The LIDAR system of claim 9, wherein the analyzer is configured tocalculate a relative range between the first location and the secondlocation at the time independent of absolute range accuracy.
 13. TheLIDAR system of claim 9, wherein the first laser subsystem is fixedlylocated with respect to the second laser subsystem.
 14. The LIDAR systemof claim 9, wherein the first range is a first estimated rangecalculated based on the first reflected laser beam and the second rangeis a second estimated range calculated based on the first reflectedlaser beam and the second reflected laser beam.
 15. The LIDAR system ofclaim 9, wherein the analyzer is further configured to: calculate afirst velocity based on a first reflected laser beam reflected from theobject in response to the first laser beam; and calculate a variation inthe first range based on a variation in the first velocity.
 16. TheLIDAR system of claim 9, wherein the analyzer is further configured to:calculate a second velocity based on a first reflected laser beamreflected from the object in response to the second laser beam; and,calculate a variation in the second range based on a variation in thesecond velocity.
 17. The LIDAR system of claim 9, wherein the analyzeris further configured to: calculate a first velocity based on a firstreflected laser beam reflected from the object in response to the firstlaser beam; and calculate a constant velocity of a surface of theobject, the analyzer is configured to correct the first velocity at thefirst location based on the constant velocity of the surface.
 18. TheLIDAR system of claim 9, wherein the analyzer is further configured to:calculate a second velocity based on a second reflected laser beamreflected from the object in response to the second laser beam; andcalculate a varying velocity of a surface of the object, the analyzer isconfigured to correct the second velocity based on the varying velocityof the surface.
 19. A method, comprising: detecting a vibration velocityfield over an object; transmitting a first laser beam at a firstlocation on the object at a time; transmitting a second laser beam at asecond location on the object at the time; generating a first rangebased on a first reflected laser beam reflected from the object inresponse to the first laser beam; generating a second range based on asecond reflected laser beam reflected from the object in response to thesecond laser beam, the first location being targeted by the first lasersubsystem and the second location being targeted by the second lasersubsystem such that a first Doppler shift for the first laser beam and asecond Doppler shift for the second laser beam are substantially thesame while the vibration velocity field is being detected.